Haptics, like the fields of
robotics and motion control, relies on high stiffness position control of
electric motors. Traditionally, DCmotors are driven by current amplifiers
designed to hide their electrical dynamics. Meanwhile encoder-based position
feedbackcreates virtual springs. Unfortunately this cancellation-replacement
approach experiences performance limits due to sensor quantization, discretization,
and amplifier bandwidths.

An alternate approachis presented,
noting the inherent inductor-resistor dynamics of the motor are beneficial
to the haptic task. Two main insights are followed, which may be utilized
independently or preferably in combination. First, the electrical inductance
L can serve as a stiffness, providing a natural sensorless coupling between
the virtual environment and the user. Second, the electrical resistance
R can create a natural wave transformation, providing a robust computer
interface between the discrete and continuous time domains. The resulting
analog circuit implements a simple voltage drive and can achieve higher
stiffness than traditional approaches, especially in the frequency range
where human users are most sensitive. Aprototype 1-DOF system has been implemented
and confirms the promise of this novel paradigm.